1. Field of the Invention
The invention relates to a packaging system with a tool for enclosing electronic components on a carrying belt, and a method of populating the carrying belt.
To enclose electronic components on a carrying or transport belt, a covering film is applied to the transport belt. The covering film covers openings on the upper side of the carrying belt, in which the electronic components to be transported are located. To enclose the electronic components, the covering film is laid over the openings and pressed onto the carrying belt with a hot tool, the openings in which the electronic components are located being sealed.
After the sealing operation, the carrying belt must comply with geometric and physical parameters predefined in accordance with the EIA Standard No. 481-1A. The pull-off force of the covering film from the carrying belt, which has to be complied with in accordance with the standard, should lie in the range of 0.1 to 1 N for the covering film, in order to be able to remove the components from the openings in the carrying belt with little expenditure of force in an automatic insertion machine. In addition, the value of the pull-off force should offer adequate security in order that the covering film cannot be detached during transport. Furthermore, the curvature over a width of the carrying belt must not exceed a limiting value. The curvature or bulging or bowing must not be greater than 1 mm over 250 mm. Therefore, the ratio of bending in millimeters to the width of the belt in millimeters must not exceed 1:250. While in the case of belts made of plastic, compliance with the limiting values of the standard is relatively unproblematic, the result is continual failures during the packaging and enclosure of electronic components in hygroscopic carrying belts.
It is accordingly an object of the invention to provide a packaging system with a tool for enclosing electronic components, and a method of populating a carrying belt that overcome the above-mentioned disadvantages of the prior art devices and methods of this general type, with which, irrespective of the carrying belt material used, reliable enclosure of the electronic components in the carrying belt can be implemented. In particular, it is an object of the invention to minimize the high failures when hygroscopic carrying belts are used.
With the foregoing and other objects in view there is provided, in accordance with the invention, a packaging system. The packaging system contains a tool for enclosing electronic components disposed in openings formed in an upper side of a carrying belt having a given width. The tool has a heatable punch with a punch face. In a rest position the punch face is disposed parallel to a covering film disposed on the carrying belt. The covering film has a width that is less than the given width of the carrying belt. The punch face has a plurality of punch face strips spaced apart from one another and are disposed so as to not overlap the openings in the carrying belt. In a sealing position of the tool, at least one of the punch face strips is disposed on the upper side of the carrying belt in a region not covered by the covering
According to the invention, the packaging system is specified with the tool for enclosing the electronic components in the carrying belt. Carrying belts of this type have on their upper side openings to accommodate individual electronic components. Such openings can be blind openings, which have been made in the carrying belt, or can be through openings, in which, before being used in a packaging system, a bottom film has been applied to the rear side of the carrying belt with the through holes, in order to close the latter on one side.
The tool of the packaging system according to the invention has a heatable punch, whose punch face, in the rest position, is disposed parallel to a covering film for the carrying belt. Here, the covering film has a smaller width than the width of the carrying belt. The punch face of the punch has, according to the invention, a plurality of punch face strips spaced apart from one another. The strips are disposed in such a way that they do not cover the openings in the carrying belt, and at least one of the punch face strips is disposed on the upper side of the carrying belt that is not covered by the covering film in the sealing position of the tool.
The subject of the invention has the advantage that not only is the region to be sealed gripped and heated by the punch face in the edge region of the openings, but also the upper side of the carrying belt not covered by the covering film is in contact with the heated punch, on account of the at least one additional punch face strip. As a result, the carrying belt is heated up relatively uniformly over its entire area, so that even carrying belts made of hygroscopic material do not distort during heating and sealing and thus remain within the specified curvature tolerance range of the EIA Standard 481-1A.
By use of the invention, the material-induced waste, in particular for belts with hygroscopic properties, is thus reduced, so that the punch face configuration supplies sealing results, irrespective of the type and the material of the carrying belt, which completely satisfy the limiting values of the above standard for carrying belts. Although the tool and the packaging system according to the invention can be used particularly advantageously for hygroscopic carrying belts, it can also be used successfully to process less hygroscopic belts, such as plastic belts.
In one embodiment of the invention, the punch face of the tool has an offset. The offset corresponds to the height difference between the upper side of the carrying belt free of covering film and the upper side of the covering film in the sealing position. The offset therefore results from a different depth formation of the punch face strips on the one hand for the upper side of the carrying belt free of covering film and on the other hand for the upper side of the covering film in the sealing position. Consequently, the offset is slightly smaller than the thickness of the covering film, specifically by the amount by which the foil reduces during sealing in the region of the punch face strips on the upper side of the covering film.
In a further embodiment of the invention, cutouts are provided between the punch face strips, a first cutout corresponding to the region of the openings in the carrying belt. In the case of this embodiment of the invention, care is advantageously taken that no punch face region is disposed over one of the openings in the carrying belt, which avoids the risk that covering film material will be pressed into the opening.
A further preferred embodiment of the invention provides for the punch face to have a cutout at the transition from the upper side of the carrying belt free of covering film to the upper side of the carrying belt covered with covering film. The cutout provides a clearance of the offset between the upper side of the carrying belt free of covering film and the upper side of the covering film in the sealing position. This makes it easier to align the covering film and the tool in the packaging system, since as a result of the clearance, a greater tolerance is permissible in aligning the covering film in the packaging system in relation to the tool and the punch face.
In addition, by the cutout at the transition from the upper side of the carrying belt free of covering film to the upper side of the covering film in the sealing position, it can be ensured that the edge of the punch face strip on the surface of the covering film does not coincide with the outer edge of the covering film or project beyond the latter. This ensures that no heat is introduced into the edge region and into the outer edges of the covering film. Introducing heat into the edges of the covering film increases the risk of stringing and of the covering film material sticking to the punch face of the tool. This risk does not arise in the packaging system according to the invention.
A further embodiment of the invention provides for the cutouts in the punch face to have different depths, the cutout depth of the cutout above the openings is greater than the cutout depth of the cutout between the upper side of the carrying belt free of the covering film and the upper side of the covering film in the sealing position. The different depths of the cutouts ensures for lower thermal coupling in the region of the openings in the carrying belt. This ensures that the coupling of heat into the covering film in the region of and over the openings in the carrying belt is low, such that incipient melting or melting of the covering film in the region of the openings is avoided, and the geometry of the covering film in the region of the openings in the carrying belt is maintained unchanged as a covering for the openings. With the lower depth of the cutout at the transition from the surface of the carrying belt free of covering film to the upper side of the covering film, it is still possible for sufficient heat to be dissipated to the upper side of the carrying belt, in order to achieve uniform heating of the carrying belt and therefore uniform drying and dehydration of hygroscopic carrying belts.
In a further embodiment of the invention, the bottom region of the punch or sealing shoe is configured with an E-shaped profile. In the case of the E-shaped profile of the sealing shoe, the result is a punch face having three punch face strips and two cutouts lying between them.
In one embodiment of the invention, a resistance heater is used as the punch heater. The resistance heater can be inserted into the punch body as a heating cartridge. This makes rapid replacement of the punch heater possible in the event of defects in the heating cartridge.
A further embodiment of the invention provides for a thermal detector to be disposed in the region of the punch face and for the packaging system to have a heat controller, which controls the punch face to a defined sealing temperature for the covering film. The heat controller has an operative connection to a power supply unit, which supplies the power for the punch heater. The heat controller is a PID controller with a proportional term P, an integral term I and a differential term D. Controllers of this type have the advantage that they react extremely quickly to temperature fluctuations and avoid overswings, so that a defined sealing temperature of the punch face can be maintained.
A further preferred embodiment of the invention provides for the punch face strips of the tool to be aligned with their length in the feed direction of the packaging system, it being possible for the length of the punch face strips to extend greater than a plurality of openings in the carrying belt. In the sealing position, the punch face strips on the covering film have a marginal spacing from the outer edges of the covering film, in order to minimize the risk of stringing.
With the foregoing and other objects in view there is further provided, in accordance with the invention, a method of populating a carrying belt with electronic components. The method includes the steps of providing a packaging system for transporting the carrying belt which has a given width, and heating up a tool of the packaging system. The tool has a punch with a punch face heated to a defined temperature and a temperature of the punch face is controllable. The punch face has a plurality of punch face strips distributed over the given width of the carrying belt. An electronic component is introduced into an opening formed in the carrying belt. A covering film is laid on the carrying belt over the opening containing the electronic component, and the covering film has a width narrower than the given width of the carrying belt.
The opening is closed by pressing the punch face, having the plurality of punch face strips, on the carrying belt having the covering film.
The method has the advantage that the entire width of the carrying belt is heated up by the punch face strips distributed over the punch face, so that the carrying belt can be heated uniformly over its entire width. On account of the uniform heating of the carrying belt in the packaging system according to the invention, in the case of the method, packaging of the electronic components is achieved without the carrying belt distorting or curving any more than is permissible after the enclosure of the electronic components in openings in the carrying belt. In addition, in the case of the method, independence of the material of the carrying belts is achieved, so that even carrying belts made of cellulosic materials like paper can be processed, without exceeding the standardized tolerance range for the permissible curvature over the width of the carrying belt, and also complying with the permissible pull-off force range of the covering film from the carrying belt after the enclosure of the electronic components.
A preferred performance example of the method provides for the temperature of the punch face to be controlled to 220xc2x0 C. to 260xc2x0 C., preferably to 240xc2x0 C. In this temperature range, it has been shown that the packaging system according to the invention, with the corresponding tool and the correspondingly structured punch face, minimizes the curvature of the carrying belt. This is achieved by the heating being carried out, with a structured punch face, both of the edge region of the openings in the transport belt covered with a covering film and the upper side of the transport belt free of covering film. It is therefore even possible for hygroscopic carrying belts made of cellulosic material to be used, since carrying belts of this type are dried uniformly and similarly by the heated punch face during the sealing operation.
In a further performance example of the method, a paper belt is used as the carrying belt and, in order to accommodate electronic components, has through openings that, on the rear side of the carrying belt, are covered by a bottom film. Such paper carrying belts have the advantage that, on account of their hygroscopic properties, they are subject to reduced electrostatic charging as compared with plastic belts. Even as a result of the brief uniform drying during the enclosure of the electronic components in the carrying belt, on account of the uniform heating of the hygroscopic carrying belts, distortion or curvature of the carrying belts can be avoided to the greatest possible extent. As a bottom film, strips of felt can be adhesively bonded onto the rear side of the carrying belt in the region of through openings in the carrying belt.
In a further performance of the method, the punch is pressed repeatedly onto the covering film in one position with 20 N to 30 N for 50 ms to 100 ms. The number of pressing and heating operations which are carried out at each component position, that is to say for each opening in the carrying belt, can be defined and optimized by the length of the punch.
In a performance example of the method, the length of the punch corresponds to a length of n positions of openings on the carrying belt. With the packaging system, following each sealing operation, the carrying belt is transported onward by one position, so that the covering film is pressed n times onto a single position for 50 ms to 100 ms in each case.
In summary, it can be recorded that, on account of asymmetrical introduction of the thermal energy into a hygroscopic carrying belt, the moisture is partly removed only in regions of the sealing operation. It is therefore necessary to expect increased curvature values or else bowing values, which restricts the use of hygroscopic belts on account of tightened permissible tolerances for automatic insertion machines. However, it is advantageous to provide a hygroscopic belt for transport, storage and processing in automatic insertion machines, since the risk of electrostatic charging of electronic components that are enclosed in hygroscopic belts is reduced as compared with plastic belts.
Although a reduction in the curvature can be established by reducing the process parameters of a packaging system in relation to the pressing pressure, the sealing time and the sealing temperature, this results in a lower pull-off force of the covering film from the carrying belt, which increases the risk of loss of components from the carrying belt during transport. By use of the packaging system according to the invention with the tool according to the invention, the necessary heat for the sealing process is distributed over the entire belt width, and therefore the heating of the carrying belt is evened out, in spite of a narrower covering film.
Furthermore, the film is not sealed over its entire area, instead no heat is introduced in the edge region of the covering film, in order that no incipient melting occurs at the sealing shoe, the bottom region of the punch. In order to equalize the sealing shoe to the film thickness, it is additionally possible for the sealing shoe to be implemented in offset form in the region of the covering film.
As a result of introducing heat over the entire area, the moisture of the belt is reduced uniformly over the entire belt width, and therefore very low curvature or bowing is achieved. The customer therefore receives a rectilinear belt, which does not have any critical problems in guides in the subsequent automatic insertion machines.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a packaging system with a tool for enclosing electronic components, and a method of populating a carrying belt, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.